Heat radiating plate and method for producing same

ABSTRACT

A heat radiating plate 10 of a metal material includes a flat plate portion 10a, a large number of columnar protruding portions 10b which protrude from one major surface of the flat plate portion and which are integrated with the flat plate portion, and a reinforcing plate member 12 of a material, which has a higher melting point than that of the flat plate portion and columnar protruding portions and which is arranged in a region, which is arranged in the flat plate portion and which is close to one major surface of the flat plate portion, the reinforcing member passing through the flat plate portion to extend in directions substantially parallel to the one major surface of the flat plate portion and having end faces exposed to the outside, the whole surface of the reinforcing member except for the end faces being bonded directly to the flat plate portion.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention generally relates to a heat radiating plate and amethod for producing the same. More specifically, the invention relatesto a heat radiating plate integrated with radiating fins, and a methodfor producing the same.

Description of the Prior Art

In a conventional Metal/ceramic bonding substrate used as an insulatingsubstrate for power modules, a metal circuit plate is bonded to one sideof a ceramic substrate, and a metal base plate for heat radiation isbonded to the other side thereof, the metal circuit plate mountingthereon semiconductor chips and so forth.

In order to radiate heat from heating elements, such as semiconductorchips, to the outside, there is known a method for mounting radiatingfins on the reverse of a metal base plate for heat radiation viaradiating grease. There is also known a method for bonding radiatingfins to a semiconductor device mounting substrate via a brazing fillermetal (see, e.g., Japanese Patent Laid-Open No. 4-363052).

In order to further improve the cooling power of a metal/ceramic bondingsubstrate, there is proposed a heat radiator which has a memberintegrated with a large number of columnar (or pillar) protrudingportions (as radiating fins), each of which has a shape of substantiallycircular truncated cone (see, e.g., Japanese Patent Laid-Open No.2007-294891).

When a large number of columnar protruding portions having a shape ofsubstantially circular truncated cone are formed as radiating fins likea heat radiator disclosed in Japanese Patent Laid-Open No. 2007-294891,if the protruding portions are formed by a method (so-called moltenmetal bonding method) for cooling and solidifying a molten metal (ofaluminum, an aluminum alloy or the like) injected into a mold, a greatthermal stress is produced during the cooling and solidifying of themolten metal by the great difference between the thermal expansioncoefficient of the mold (of isotropic carbon or the like) and that ofaluminum, the aluminum alloy or the like, so that it is very difficultto release the protruding portions from the mold if a large number ofradiating fins having a small tapered angle (of not greater than 5°) areformed to increase the total surface area of the radiating fins. Forthat reason, there are problems in that it is not possible to obtainradiating fins having a desired shape due to the flaws and breaksthereof and/or that the mold is broken.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to eliminate theaforementioned problems and to provide a heat radiating plate, which canbe easily released from a mold to form columnar (or pillar) protrudingportions having a desired shape while preventing the break of the mold,even if the heat radiating plate produced by the mold has a flat plateportion integrated with a large number of protruding portions whichprotrude from one major surface of the flat plate portion, and a methodfor producing the same.

In order to accomplish the aforementioned and other objects, theinventors have diligently studied and found that it is possible toproduce a heat radiating plate, which can be easily released from a moldto form columnar (or pillar) protruding portions having a desired shapewhile preventing the mold from being broken, even if the heat radiatingplate produced by the mold has a flat plate portion integrated with alarge number of protruding portions which protrude from one majorsurface of the flat plate portion, if a reinforcing member extending indirections substantially parallel to the one major surface of the flatplate portion is arranged in a region which is arranged in the flatplate portion and which is close to the one major surface of the flatplate portion, in the heat radiating plate which is made of a metal andwhich has the flat plate portion integrated with the large number ofprotruding portions which protrude from the one major surface of theflat plate portion. Thus, the inventors have made the present invention.

According to one aspect of the present invention, there is provided aheat radiating plate which is made of a metal material and whichcomprises: a flat plate portion; a large number of columnar protrudingportions which protrude from one major surface of the flat plate portionand which are integrated with the flat plate portion; and a reinforcingmember which extends in directions substantially parallel to one majorsurface of the flat plate portion, the reinforcing member being arrangedin a region which is arranged in the flat plate portion and which isclose to the one major surface of the flat plate portion.

In this heat radiating plate, the reinforcing member preferably passesthrough the flat plate portion to extend therein, and the whole surfaceof a portion of the reinforcing member passing through the flat plateportion to extend therein is preferably bonded directly to the flatplate portion. The reinforcing member preferably has end faces which areexposed to the outside, and the whole surface of the reinforcing memberexcept for the end faces is preferably bonded directly to the flat plateportion. The reinforcing member is preferably a plate member, and may bea plurality of plate members which are spaced from each other to extend.The reinforcing member is made of a material which has a higher meltingpoint than that of the metal material of the flat plate portion and thecolumnar protruding portions. The metal material of the flat plateportion and the columnar protruding portion is preferably aluminum or analuminum alloy. In this case, the reinforcing member is preferably madeof a metal which contains iron and at least one selected from the groupconsisting of nickel, cobalt, copper and manganese. Alternatively, thereinforcing member may be made of at least one ceramic selected from thegroup consisting of alumina, aluminum nitride, silicon nitride andsilicon carbide. Each of the large number of columnar protrudingportions preferably has a shape of substantially cylindrical or circulartruncated cone, and may have a shape of substantially rectangular columnor flat plate. The region close to the one major surface of the flatplate portion is preferably a region which is apart from the one majorsurface of the flat plate portion by 0.1 to 1.0 mm. One major surface ofa ceramic substrate may be bonded directly to the other major surface ofthe flat plate portion, and a metal plate may be bonded directly to theother major surface of the ceramic substrate.

According to another aspect of the present invention, there is provideda method for producing a heat radiating plate which is made of a metalmaterial and which has a flat plate portion and a large number ofcolumnar protruding portions protruding from one major surface of theflat plate portion and being integrated with the flat plate portion, themethod comprising the steps of: allowing end portions of a reinforcingmember of a material, which has a higher melting point than that of theflat plate portion and the columnar protruding portions, to be supportedon a mold; injecting a molten metal of a metal material into the mold sothat the molten metal contacts the whole surface of the reinforcingmember except for end portions thereof in the mold; and then, coolingand solidifying the molten metal for forming the flat plate portion andthe large number of columnar protruding portions, which protrude fromthe one major surface of the flat plate portion and which are integratedwith the flat plate portion, and for allowing the reinforcing member,which extends substantially parallel to the one major surface of theflat plate portion, to be arranged in a region, which is arranged in theflat plate portion and which is close to the one major surface of theflat plate portion, while allowing the reinforcing member to be bondeddirectly to the flat plate portion.

According to a further aspect of the present invention, there isprovided a method for producing a heat radiating plate which is made ofa metal material and which has a flat plate portion and a large numberof columnar protruding portions protruding from one major surface of theflat plate portion and being integrated with the flat plate portion, theother major surface of the flat plate portion being bonded directly toone major surface of a ceramic substrate, the method comprising thesteps of: allowing end portions of the ceramic substrate and endportions of a reinforcing member of a material, which has a highermelting point than that of the flat plate portion and the columnarprotruding portions, to be supported on a mold so that the ceramicsubstrate is apart from the reinforcing member in the mold; injecting amolten metal of a metal material into the mold so that the molten metalcontacts both major surfaces of the substrate and the whole surface ofthe reinforcing member except for end portions thereof in the mold; andthen, cooling and solidifying the molten metal for forming a metal plateto allow the metal plate to be bonded directly to the other majorsurface of the ceramic substrate, and for forming the flat plate portionand the large number of columnar protruding portions, which protrudefrom the one major surface of the flat plate portion and which areintegrated with the flat plate portion, and for allowing the reinforcingmember, which extends substantially parallel to the one major surface ofthe flat plate portion, to be arranged in a region, which is arranged inthe flat plate portion and which is close to the one major surface ofthe flat plate portion, while allowing the reinforcing member to bebonded directly to the flat plate portion.

In these methods for producing a heat radiating plate, the reinforcingmember preferably passes through the flat plate portion to extendtherein, and the whole surface of a portion of the reinforcing memberpassing through the flat plate portion to extend therein is preferablybonded directly to the flat plate portion. The end portions of thereinforcing member protruding from the flat plate portion are preferablyremoved. The mold preferably comprises an upper mold member and a lowermold member, and the end portions of the reinforcing member arepreferably clamped between the upper mold member and the lower moldmember to be supported on the mold. The reinforcing member is preferablya plate member, and may be a plurality of plate members which are spacedfrom each other to extend. The molten metal is a molten metal ofaluminum or an aluminum alloy. In this case, the reinforcing member ispreferably made of a metal which contains iron and at least one selectedfrom the group consisting of nickel, cobalt, copper and manganese.Alternatively, the reinforcing member may be made of at least oneceramic selected from the group consisting of alumina, aluminum nitride,silicon nitride and silicon carbide. Each of the large number ofcolumnar protruding portions preferably has a shape of substantiallycylindrical or circular truncated cone, and may have a shape ofsubstantially rectangular column or flat plate. The region close to theone major surface of the flat plate portion is preferably a region whichis apart from the one major surface of the flat plate portion by 0.1 to1.0 mm.

According to the present invention, it is possible a heat radiatingplate, which can be easily released from a mold to form columnar (orpillar) protruding portions having a desired shape while preventing thebreak of the mold, even if the heat radiating plate produced by the moldhas a flat plate portion integrated with a large number of protrudingportions which protrude from one major surface of the flat plateportion.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood more fully from the detaileddescription given herebelow and from the accompanying drawings of thepreferred embodiments of the invention.

However, the drawings are not intended to imply limitation of theinvention to a specific embodiment, but are for explanation andunderstanding only.

In the drawings:

FIG. 1A is a perspective view of the first preferred embodiment of aheat radiating plate according to the present invention;

FIG. 1B is a plan view of the heat radiating plate of FIG. 1A;

FIG. 1C is a sectional view taken along line IC-IC of FIG. 1B;

FIG. 2A is a sectional view of a mold used for producing the heatradiating plate shown in FIGS. 1A through 1C;

FIG. 2B is a perspective view of a lower mold member of the mold of FIG.2A;

FIG. 2C is a plan view of the lower mold member of the mold of FIG. 2A;

FIG. 2D is a bottom view of an upper mold member of the mold of FIG. 2A;

FIG. 3A is a sectional view of the second preferred embodiment of a heatradiating plate according to the present invention;

FIG. 3B is a plan view of the heat radiating plate of FIG. 3A (on theside of a metal/ceramic bonding substrate);

FIG. 4A is a sectional view of a mold used for producing the heatradiating plate shown in FIGS. 3A and 3B;

FIG. 4B is a perspective view of a lower mold member of the mold of FIG.4A;

FIG. 4C is a plan view of the lower mold member of the mold of FIG. 4A;

FIG. 4D is a bottom view of an upper mold member of the mold of FIG. 4A;

FIG. 5A is a perspective view of the third preferred embodiment of aheat radiating plate according to the present invention;

FIG. 5B is a plan view of the heat radiating plate of FIG. 5A (on theside of columnar protruding portions);

FIG. 6 is a plan view of a first modified example of columnar protrudingportions of a heat radiating plate in the first through third preferredembodiments; and

FIG. 7 is a plan view of a second modified example of columnarprotruding portions of a heat radiating plate in the first through thirdpreferred embodiments.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the accompanying drawings, the preferred embodiments ofa heat radiating plate and a method for producing the same according tothe present invention will be described below in detail.

First Preferred Embodiment

FIGS. 1A through 1C show the first preferred embodiment of a heatradiating plate according to the present invention. FIG. 1A is aperspective view of a heat radiating plate in this preferred embodiment,FIG. 1B is a plan view of the heat radiating plate of FIG. 1A, and FIG.1C is a sectional view taken along line IC-IC of FIG. 1B.

In this preferred embodiment, a heat radiating plate 10 is made of ametal material, such as aluminum or an aluminum alloy. As shown in FIGS.1A through 1C, the heat radiating plate 10 comprises: a flat plateportion 10 a having a substantially rectangular planar shape; a largenumber of columnar (or pillar) protruding portions 10 b (serving asradiating fins) integrated with the flat plate portion 10 a so as toprotrude from one major surface of the flat plate portion 10 a; and oneor a plurality of reinforcing plate members (three elongated reinforcingplate members having rectangular planar and sectional shapes in thispreferred embodiment) 12 of a metal or ceramic, which are arranged inthe flat plate portion 10 a.

Each of the columnar protruding portions 10 b has a shape ofsubstantially cylindrical or circular truncated cone (a shape obtainedby cutting the upper end portion of a substantially circular cone indirections substantially parallel to the bottom face thereof). Theprotruding portions 10 b extend in directions substantiallyperpendicular to the major surface of the flat plate portion 10 a. Thecolumnar protruding portions 10 b are arranged as a plurality of rows ofcolumnar protruding portions 10 b. In each row, the columnar protrudingportions 10 b are arranged at regular intervals. Each row of thecolumnar protruding portions 10 b linearly extends, and the rows of thecolumnar protruding portions 10 b are arranged in parallel to eachother. Adjacent two rows of the columnar protruding portions 10 b arearranged so as to be shifted from each other by a half pitch (by half ofa distance between the central lines (axes of the columnar protrudingportions 10 b) of adjacent two rows of the columnar protruding portions10 b). Thus, the larger number of columnar protruding portions 10 b arearranged so that the distance between the adjacent two of the columnarprotruding portions 10 b is ensured. If the larger number of columnarprotruding portions 10 b can be arranged so that the distance betweenthe adjacent two of the columnar protruding portions 10 b is ensured,other arrangement may be adapted.

In this preferred embodiment, the flat plate portion 10 a has athickness of about 3 to 10 mm. Each of the columnar protruding portions10 b has, e.g., a root diameter (a diameter of the bottom face thereof)of 1 to 10 mm, preferably 1.5 to 8 mm, and a height of about 2 to 50 mm,preferably about 5 to 15 mm. The columnar protruding portions 10 b arearranged at intervals (or pitches) of about 2 to 10 mm, preferably about3 to 7 mm (so as to be apart from each other by a distance about 2 to 10mm, preferably about 3 to 7 mm, between the central lines of adjacentcolumnar protruding portions 10 b). Each of the columnar protrudingportions 10 b has a tapered angle (an angle between the central line ofeach of the columnar protruding portions 10 b and the side face thereof)of 0.5 to 5°, preferably 1 to 3°. The number of the columnar protrudingportions 19 b is, e.g., preferably about 20 to 1000, more preferably 50to 1000.

The reinforcing members 12 pass through the interior of the flat plateportion 10 a from one of both end faces in width directions (lateraldirections perpendicular to longitudinal directions and thicknessdirections) thereof to the other end face to extend in the widthdirections. The reinforcing members 12 are arranged in a region (aregion close to a highest stress region between the heat radiating plate10 and a mold 20 shown in FIGS. 2A through 2D), which is close to onemajor surface (a major surface on the side of the columnar protrudingportions 10 b) of the flat plate portion 10 b of the heat radiatingplate 10, so that the (apparent) thermal expansion coefficient of theone major surface (the major surface on the side of the columnarprotruding portions 10 b) of the flat plate portion 10 a of the heatradiating plate approaches that of the mold 20. The reinforcing members12 are preferably arranged in a region which is apart from the one majorsurface (the major surface on the side of the columnar protrudingportions 10 b) of the flat plate portion 10 a by 20% or less of thethickness of the flat plate portion 10 a. In this preferred embodiment,the reinforcing members 12 are arranged in a region which is apart fromthe one major surface of the flat plate portion 10 b by a distance ofpreferably 0.1 to 1.0 mm, more preferably 0.15 to 0.8 mm, and mostpreferably 0.2 to 0.7 mm (since the distance is preferably 0.2 mm ormore in order to allow the molten metal to be easily injected into themold).

The both end faces of the reinforcing members 12 in longitudinaldirections thereof (in width directions of the flat plate portion 10 a)are exposed to the outside. The whole surface of each of the reinforcingmembers 12 except for the both end faces thereof (the whole surface of aportion of each of the reinforcing members 12 passing through the flatplate portion 10 a to extend therein) is bonded directly to the flatplate portion 10 a. Thus, the reinforcing members 12 passing through theflat plate portion 10 a from one of both end faces in width directionsthereof to the other end face to extend in the width directions areprovided in the region close to the one major surface (the major surfaceon the side of the columnar protruding portions 10 b) of the flat plateportion 10 a, so that it is possible to easily release the heatradiating plate 10 from the mold 20 after the heat radiating plate 10 isproduced by the mold 20.

Furthermore, the flat plate portion 10 a and the columnar protrudingportions 10 b integrated therewith are preferably made of aluminum or analuminum alloy from the standpoints of electric conductivity, thermalconductivity and reliability of bonding to a ceramic substrate (when theceramic substrate is bonded to the other major surface of the flat plateportion 10 a of the heat radiating plate 10). The reinforcing members 12are preferably made of a material which has a higher melting point thanthat of the flat plate portion 10 a and columnar protruding portions 10b. If the reinforcing members 12 are made of a metal material, they arepreferably made of a steel or iron containing metal, which isinexpensive and which has a high strength. The iron containing metal ispreferably a metal which contains iron and at least one selected fromthe group consisting of nickel, cobalt, copper and manganese. If thereinforcing members 12 are made of a ceramic material, they arepreferably made of at least one selected from the group consisting ofalumina, aluminum nitride, silicon nitride and silicon carbide, and morepreferably aluminum nitride in view of the heat radiating performancethereof.

The heat radiating plate 10 in the preferred embodiment shown in FIGS.1A through 1C can be produced by a method comprising the steps of:allowing both end portions of each of the reinforcing members 12 inlongitudinal directions thereof to be supported on the mold 20 so as toarrange the reinforcing members 12 in the mold 20 shown in FIGS. 2Athrough 2D; injecting a molten metal into the mold 20 so that the moltenmetal contacts the whole surface of each of the reinforcing members 12except for both end portions in longitudinal directions thereof; andthen, cooling the mold 20.

As shown in FIG. 2A, the mold 20 of carbon or the like comprises a lowermold member 22 and an upper mold member 24, each of which has asubstantially rectangular planar shape.

As shown in FIGS. 2A through 2C, the top face of the lower mold member22 has a recessed portion (a flat plate forming portion) 22 a forforming a portion of the flat plate portion 10 a on the side of theother major surface (the major surface on the opposite side to thecolumnar protruding portions 10 b) thereof. The upper portion of each ofboth side faces of the flat plate forming portion 22 a in widthdirections thereof has recessed portions (reinforcing member supportingportions) 22 b, each of which substantially has the same shape and sizeas those of a corresponding one of both end portions of a correspondingone of the reinforcing members 12 in longitudinal directions thereof andwhich are spaced from each other, for housing therein the both endportions thereof.

As shown in FIGS. 2A and 2D, the under surface (reverse face) of theupper mold member 24 has a recessed portion (a flat plate formingportion) 24 a for forming a portion of the flat plate portion 10 a onthe side of the one major surface (the major surface on the side of thecolumnar protruding portions 10 b) thereof (a portion of the flat plateportion 10 a nearer to the columnar protruding portions 10 b than thereinforcing members 12). The bottom face of the recessed portion 24 ahas a large number of recessed portions (columnar protrusion formingportions) 24 b for forming a large number of columnar protrudingportions 10 b. The flat plate portion 10 a is designed to be formed in aspace defined by the flat plate forming portion 24 a of the upper moldmember 24 and the flat plate forming portion 22 a of the lower moldmember 22. The reinforcing members 12 are designed to be clamped betweenthe upper mold member 24 and the reinforcing member supporting portions22 b of the lower mold member 22 when the lower mold member 22 iscovered with the upper mold member 24 after the reinforcing members 12are housed in the reinforcing member supporting portions 22 b of thelower mold member 22. When the reinforcing members 12 are thus clamped,it is possible to precisely fix the reinforcing members 12 atpredetermined positions (at predetermined positions in directions alongthe major surface of the flat plate portion 10 a and in thicknessdirections thereof). The distance (the width of the flat plate portion22 a) between the reinforcing member supporting portions 22 b forsupporting both end portions of each of the reinforcing members 12 ispreferably such a length that a corresponding one of the reinforcingmembers 12 is not deflected by the molten metal in the mold 20. Forexample, the distance is preferably 75 mm or less when the thickness ofeach of the reinforcing members 12 is 0.6 mm, and it may be longer wheneach of the reinforcing members 12 is thicker. Furthermore, the lowermold member 22 or the upper mold member 24 has an inlet (not shown) forinjecting a molten metal into the flat plate forming portion 24 a froman injecting nozzle (not shown).

In order to use such a mold 20 for producing the preferred embodiment ofa heat radiating plate shown in FIG. 1A through 1C, the reinforcingmembers 12 are put on the reinforcing member supporting portions 22 b ofthe lower mold member 22, and then, the lower mold member 22 is coveredwith the upper mold member 24. In this state, if a molten metal ofaluminum, an aluminum alloy or the like is injected into the mold 20 andcooled, it is possible to produce the heat radiating plate wherein thereinforcing members 12 are arranged in the flat plate portion 10 a,wherein both end portions of the reinforcing members 12 in longitudinaldirections thereof protrude from the side faces of the flat plateportion 10 a, and wherein the columnar protruding portions 10 b areintegrated with one major surface of the flat plate portion 10 a.Thereafter, the both end portions of each of the reinforcing members 12in the longitudinal directions thereof, the both end portions protrudingfrom the flat plate portion 10 a, are cut by a well-known cuttingmethod, so that it is possible to produce the heat radiating plate 10 inthe preferred embodiment shown in FIGS. 1A through 1C. Furthermore, ifdividing grooves (break lines) are previously and precisely formed atthe cutting portions of the reinforcing members 12 by means of a laser,a scriber or the like, it is possible to easily divide and remove theboth end portions of the reinforcing members 12 (by hand).

The molten metal is preferably injected into the mold 20 as follows.First, the mold 20 is moved into a furnace (not shown), and the interiorof the furnace is caused to be in an atmosphere of nitrogen to decreasethe oxygen concentration therein to 100 ppm or less, preferably 10 ppmor less. Then, the mold 20 is heated to a molten metal injectingtemperature (e.g., 600 to 800° C. when a molten metal of aluminum or analuminum alloy is injected) by the temperature control of a heater.Thereafter, while oxide films on the surface of a molten metal areremoved, the molten metal, which is heated to the molten metal injectingtemperature and which is previously measured, is pressurized at apredetermined pressure by nitrogen gas to be injected into the mold 20from the inlet. After the molten metal is injected into the mold 20,nitrogen gas is preferably blown into the inlet from a nozzle (notshown) to cool and solidify the molten metal in the mold 20 whilepressurizing the molten metal therein at a predetermined pressure. Thepredetermined pressure applied by nitrogen gas during the injection andcooling of the molten metal is preferably in the range of from 1 kPa to100 kPa, more preferably in the range of from 3 kPa to 80 kPa, and mostpreferably in the range of from 5 kPa to 15 kPa. If the pressure is toolow, it is difficult to allow the molten metal to be injected into themold 20 (particularly into the columnar protrusion forming portions 24 bof the mold 20). If the pressure is too high, there is some possibilitythat the positions of the reinforcing members 12 may be shifted and/orthe mold 20 may be broken. In particular, when a high pressure of notless than 1 MPa is applied if the mold 20 of carbon is used, there issome possibility that the mold 20 may be broken and/or the molten metalmay leak from the mold 20 and/or the positions of the reinforcingmembers 12 may be shifted.

In this preferred embodiment, it is possible to radiate heat fromheating elements if parts required to radiate heat from the heatingelements, such as a metal/ceramic bonding substrate mounting thereonsemiconductor chips and so forth, are mounted on the other major surface(the major surface on the opposite side to the columnar protrudingportions 10 b) of the flat plate portion 10 a of the heat radiatingplate 10.

Second Preferred Embodiment

FIGS. 3A and 3B show the second preferred embodiment of a heat radiatingplate according to the present invention. FIG. 3A is a sectional view ofthe heat radiating plate in this preferred embodiment, and FIG. 3B is aplan view of the heat radiating plate of FIG. 3A (on the side of ametal/ceramic bonding substrate).

In this preferred embodiment, the same heat radiating plate as that inthe first preferred embodiment is bonded to and integrated with partsrequired to radiate heat from the heating elements, such as ametal/ceramic bonding substrate mounting thereon semiconductor chips andso forth.

In this preferred embodiment, as shown in FIGS. 3A and 3B, a largenumber of columnar protruding portions 110 b are formed on one majorsurface of a flat plate portion 110 a of a heat radiating plate 110, andreinforcing members 112 are arranged in the flat plate portion 110 athereof. One major surface of at least one (one in this preferredembodiment) ceramic substrate 114 is bonded to the other major surface(the major surface on the opposite side to the columnar protrudingportions 110 b) of the flat plate portion 110 a of the heat radiatingplate 110. The other major surface of the ceramic substrate 114 isbonded to a metal plate 116. Thus, the heat radiating plate 110 isintegrated with and bonded to the metal/ceramic bonding substratewherein the metal plate 116 is bonded to the ceramic substrate 114. Whenthe metal/ceramic bonding substrate is integrated with and bonded to theheat radiating plate 110 as this preferred embodiment, the reinforcingmembers 112 are preferably arranged in a region which is apart from theone major surface (the major surface on the side of the columnarprotruding portions 110 b) by a distance of 0.5 to 2.5 times as long asthe thickness of the metal plate 116, and more preferably arranged in aregion which is apart from the one major surface by a distance of 0.7 to2 times as long as the thickness of the metal plate 116. Furthermore, inFIGS. 3A and 3B and in FIGS. 4A through 4D which will be describedlater, 100 is added to each of the reference numbers of portions havingthe same constructions as those of the heat radiating plate 10 in theabove-described preferred embodiment.

The heat radiating plate 110 thus integrated with and bonded to themetal/ceramic bonding substrate can be produced by a method comprisingthe steps of: allowing the peripheral portion of the ceramic substrate114 and both end portions of each of the reinforcing members 112 inlongitudinal directions thereof to be supported on a mold 120 so as toarrange the ceramic substrate 114 and the reinforcing members 112 at apredetermined interval in the mold 120 shown in FIGS. 4A through 4D;injecting a molten metal into the mold 120 so that the molten metalcontacts both sides of the ceramic substrate 114 and the whole surfaceof each of the reinforcing members 112 except for both end portions inlongitudinal directions thereof; and then, cooling the mold 120.

As shown in FIG. 4A, the mold 120 of carbon or the like comprises alower mold member 122 and an upper mold member 124, each of which has asubstantially rectangular planar shape.

As shown in FIGS. 4A through 4C, the top face of the lower mold member122 has a recessed portion (a flat plate forming portion) 122 a forforming a portion of the flat plate portion 110 a on the side of theother major surface (the major surface on the opposite side to thecolumnar protruding portions 110 b) thereof. The bottom face of therecessed portion 122 a has a recessed portion (a ceramic substratehousing portion) 122 c, which substantially has the same shape and sizeas those of the ceramic substrate 114, for housing therein the ceramicsubstrate 114. The bottom face of the recessed portion 122 c has arecessed portion (a metal plate forming portion) 122 d for forming ametal plate 116 for a circuit pattern. The upper portion of each of bothside faces of the flat plate forming portion 122 a in width directionsthereof has recessed portions (reinforcing member supporting portions)122 b, each of which substantially has the same shape and size as thoseof a corresponding one of both end portions of a corresponding one ofthe reinforcing members 112 in longitudinal directions thereof and whichare spaced from each other, for housing therein the both end portionsthereof.

As shown in FIGS. 4A and 4D, the under surface (reverse face) of theupper mold member 124 has a recessed portion (a flat plate formingportion) 124 a for forming a portion of the flat plate portion 110 a onthe side of the one major surface (the major surface on the side of thecolumnar protruding portions 110 b) thereof (a portion of the flat plateportion 110 a nearer to the columnar protruding portions 110 b than thereinforcing members 112). The bottom face of the recessed portion 124 ahas a large number of recessed portions (columnar protrusion formingportions) 124 b for forming a large number of columnar protrudingportions 110 b. The flat plate portion 110 a is designed to be formed ina space defined by the flat plate forming portion 124 a of the uppermold member 124 and the flat plate forming portion 122 a of the lowermold member 122. The reinforcing members 112 are designed to be clampedbetween the upper mold member 124 and the reinforcing member supportingportions 122 b of the lower mold member 122 when the lower mold member122 is covered with the upper mold member 124 after the reinforcingmembers 112 are housed in the reinforcing member supporting portions 122b of the lower mold member 122. When the reinforcing members 112 arethus clamped, it is possible to precisely fix the reinforcing members112 at predetermined positions (at predetermined positions in directionsalong the major surface of the flat plate portion 110 a and in thicknessdirections thereof). The distance (the width of the flat plate portion122 a) between the reinforcing member supporting portions 122 b forsupporting both end portions of each of the reinforcing members 112 ispreferably such a length that a corresponding one of the reinforcingmembers 112 is not deflected by the molten metal in the mold 120. Forexample, the distance is preferably 75 mm or less when the thickness ofeach of the reinforcing members 112 is 0.6 mm, and it may be longer wheneach of the reinforcing members 112 is thicker.

The upper mold member 124 has an inlet (not shown) for injecting amolten metal into the flat plate forming portion 129 a from an injectingnozzle (not shown). The lower mold member 122 has a molten metal passage(not shown) which extends between the flat plate forming portion 122 aand the metal plate forming portion 122 d for establishing acommunication between the flat plate forming portion 122 a and the metalplate forming portion 122 d even if the ceramic substrate 114 is housedin the ceramic substrate housing portion 122 c.

In order to use such a mold 120 for producing a heat radiating plate110, which is integrated with and bonded to a metal/ceramic bondingsubstrate, as shown in FIGS. 3A and 3B, after the ceramic substrate 114is arranged in the ceramic substrate housing portion 122 c of the lowermold member 122, the reinforcing members 112 are put on the reinforcingmember supporting portions 122 b of the lower mold member 122, and then,the lower mold member 122 is covered with the upper mold member 124. Inthis state, if a molten metal of aluminum, an aluminum alloy or the likeis injected into the mold 120 and cooled, it is possible to produce theheat radiating plate 110 which is integrated with and bonded to themetal/ceramic bonding substrate, wherein both end portions of each ofthe reinforcing members 112 in longitudinal directions thereof, thereinforcing members 112 being arranged in the flat plate portion 110 a,protrude from the side faces of the flat plate portion 110 a and whereinthe columnar protruding portions 110 b are integrated with one majorsurface of the flat plate portion 110 a, the other major surface thereofbeing bonded directly to one side of the ceramic substrate 114, theother side thereof being bonded directly to the metal plate 116 for acircuit pattern. Thereafter, the both end portions of each of thereinforcing members 112 in the longitudinal directions thereof, the bothend portions protruding from the flat plate portion 110 a, are cut by awell-known cutting method, so that it is possible to produce the heatradiating plate 110 in the preferred embodiment shown in FIGS. 3Athrough 3C.

The molten metal is preferably injected into the mold 120 as follows.First, the mold 120 is moved into a furnace (not shown), and theinterior of the furnace is caused to be in an atmosphere of nitrogen todecrease the oxygen concentration therein to 100 ppm or less, preferably10 ppm or less. Then, the mold 120 is heated to a molten metal injectingtemperature (e.g., 600 to 800 when a molten metal of aluminum or analuminum alloy is injected) by the temperature control of a heater.Thereafter, the molten metal, which is heated to the molten metalinjecting temperature and which is previously measured, is pressurizedat a predetermined pressure by nitrogen gas to be injected into the mold120 from the inlet. If the molten metal is thus injected, it is possibleto prevent large bonding defects from being produced between the metaland the ceramic. After the molten metal is injected into the mold 120,nitrogen gas is preferably blown into the inlet from a nozzle (notshown) to cool and solidify the molten metal in the mold 120 whilepressurizing the molten metal therein at a predetermined pressure. Thepredetermined pressure applied by nitrogen gas during the injection andcooling of the molten metal is preferably in the range of from 1 kPa to100 kPa, more preferably in the range of from 3 kPa to 80 kPa, and mostpreferably in the range of from 5 kPa to 15 kPa. If the pressure is toolow, it is difficult to allow the molten metal to be injected into themold 120. If the pressure is too high, there is some possibility thatthe positions of the reinforcing members 12 may be shifted and/or themold 120 may be broken. In particular, when a high pressure of not lessthan 1 MPa is applied if the mold 120 of carbon is used, there is somepossibility that the mold 120 may be broken and/or the molten metal mayleak from the mold 120 and/or the positions of the reinforcing members112 and ceramic substrate 114 may be shifted.

In order to form a metal circuit plate from the metal plate 116 of themetal/ceramic bonding substrate thus integrated with and bonded to theheat radiating plate 110, the metal plate 116 may be etched to form acircuit pattern. In order to enable the circuit pattern to be soldered,the circuit pattern may be coated with Ni plating or Ni alloy plating.

Third Preferred Embodiment

FIGS. 5A and 5B show the third preferred embodiment of a heat radiatingplate according to the present invention. FIG. 5A is a perspective viewof the heat radiating plate in this preferred embodiment, and FIG. 5B isa plan view of the heat radiating plate of FIG. 5A (on the side ofcolumnar protruding portions).

In this preferred embodiment, as shown in FIGS. 5A and 5B, columnarprotruding portions 210 b may be formed on one major surface of a flatplate portion 210 a of a heat radiating plate 210 so as to correspond toregions (heating element mounting regions) 218 (on the other majorsurface of the flat plate portion 210 a) on which parts required toradiate heat from heating elements, such as a metal/ceramic bondingsubstrate mounting thereon semiconductor chips and so forth, arearranged. Furthermore, in FIGS. 5A and 5B, 200 is added to each of thereference numbers of portions having the same constructions as those ofthe heat radiating plate 10 in the above-described preferred embodiment.

While each of the columnar protruding portions 10 b, 110 b and 210 b hasa shape of substantially cylindrical or circular truncated cone in theabove-described first through third preferred embodiments, it may have ashape of substantially rectangular column as shown in FIG. 6, or it mayhave a shape of substantially flat plate as shown in FIG. 7.Furthermore, in FIGS. 6 and 7, 300 and 400 are added to each of thereference numbers of portions having the same constructions as those inthe above-described preferred embodiment, respectively.

While each of the heat radiating plates uses an air-cooled radiatingfins (columnar protruding portions 10 b, 110 b, 210 b) in theabove-described first through third preferred embodiments, each of thecolumnar protruding portions 10 b, 110 b and 210 b may be covered with acasing (not shown) to forma water-cooled heat radiator, in which acooling fluid flows, in order to enhance the cooling power thereof.

Examples of a heat radiating plate and a method for producing the sameaccording to the present invention will be described below in detail.

Example 1

First, there was prepared a mold of carbon having a similar shape tothat of the mold 120 shown in FIGS. 4A through 4D, except that thenumber of reinforcing member supporting portions 122 b was changed fromthree pairs to one pair. There were also prepared a ceramic substrate114 of aluminum nitride having a size of 90 mm×40 mm×0.6 mm, and areinforcing member 112 of aluminum nitride having a size of 90 mm×56mm×0.6 mm. Then, the ceramic substrate 114 was arranged in the ceramicsubstrate housing portion 122 c of the lower mold member 122 of the mold120, and both end portions (having a length of 3 mm) of the reinforcingmember 112 were arranged in the reinforcing member supporting portions122 b of the lower mold member 122, respectively. Thereafter, the lowermold member 122 was covered with the upper mold member 124 of the mold120 to be put in a furnace, and the interior of the furnace was causedto be in an atmosphere of nitrogen to decrease the oxygen concentrationtherein to 4 ppm or less. In this state, the mold 120 was heated to 720°C. by the temperature control of a heater, and then, a molten metal ofaluminum having a purity of 99.9%, which was heated to 720° C. andpreviously measured, was poured into the mold 120 from the injectingnozzle mounted on the inlet of the mold 120 while being pressurized at10 kPa by nitrogen gas to remove oxide films on the surface of themolten metal. Thus, the molten metal was filled in a space having a sizeof 115 mm×50 mm×5 mm defined by the flat plate forming port ion 122 aand the flat plate forming portion 124 a (having a depth of 0.4 mm) inthe mold 120, and in the metal plate forming portion 122 d having a sizeof 88 mm×38 mm×0.4 mm via the molten metal passage formed in the lowermold member 122. Thereafter, nitrogen gas was blown into the inlet fromthe injecting nozzle to cool and solidify the molten metal in the mold120 while pressurizing the molten metal at 10 kPa. Thus, by a so-calledmolten metal bonding method, there was produced a heat radiating platewherein the reinforcing member 112 passed through the flat plate,portion 110 a in a region, in which one major surface of the reinforcingmember 112 (the major surface on the side of the columnar protrudingportions 110 b) was spaced from one major surface of the flat plateportion 110 a (the major surface on the side of the columnar protrudingportions 110 b) by 0.4 mm, the reinforcing member 112 being bondeddirectly to the flat plate portion 110 a, both end portions of thereinforcing member 112 protruding from the side faces of the flat plateportion 110 a, wherein 128 columnar protruding portions 110 b werearranged on one major surface of the flat plate portion 110 a atintervals (pitches) of 5 mm, each of the columnar protruding portions110 b having a shape of substantially circular truncated cone which hada root diameter (a diameter of a bottom face) of 4 mm, a height of 8 mmand a tapered angle of 2° (the total surface area of the columnarprotruding portions 110 b being 7628 mm²), and wherein one major surfaceof the ceramic substrate 114 was bonded directly to the other majorsurface of the flat plate portion 110 a, and the metal plate 116 wasbonded directly to the other major surface of the ceramic substrate 114.After the heat radiating plate was ejected from the mold 120, the bothend portions of the reinforcing members 112 in longitudinal directionsthereof, the end portions protruding from the flat plate portion 110 a,were removed (by dividing the both end portions by hand along breaklines previously formed by laser processing) to produce a heat radiatingplate 110 having a similar shape to that shown in FIGS. 3A and 3B.

Furthermore, when the heat radiating plate was ejected from the mold120, after the lower mold member 122 was detached, the upper mold member124 was fixed to a mold releasing apparatus, and a steel plate wasarranged on the upper mold member 124 so as to contact thereto. Then,the steel plate was knocked by a knocker (for quantitatively makingshocks on the mold to release the heat radiating plate from the mold) toevaluate the releasability of the heat radiating plate from the mold bythe number of shocks until release, and the surfaces of the heatradiating plate and the mold were observed. As a result, it was possibleto release the heat radiating plate from the mold by two shocks. Therewas no problem in the shapes of the flat plate portion and columnprotruding portions of the heat radiating plate, and the mold was notdamaged.

Examples 2-4

There was produced a heat radiating plate 110 by the same method as thatin Example 1, except that the columnar protruding portions 110 b had aheight of 5 mm, a tapered angle of 5° and a total surface area of 5018mm² in Example 2, that the columnar protruding portions 110 b had aheight of 5 mm, a tapered angle of 3° and a total surface area of 5235mm² in Example 3, and that the columnar protruding portions 110 b had aheight of 5 mm and a total surface area of 5364 mm² in Example 4. Then,by the same method as that in Example 1, the releasability of the heatradiating plate was evaluated, and the surfaces of the heat radiatingplate and the mold were observed. Asa result, it was possible to releasethe heat radiating plate from the mold by no shock (Example 2), oneshock (Example 3) and two shocks (Example 4), respectively. In Examples2 through 4, there was no problem in the shapes of the flat plateportion and column protruding portions of the heat radiating plate, andthe mold was not damaged.

Examples 5-8

There was produced a heat radiating plate 110 by the same method as thatin Example 1, except that the columnar protruding portions 110 b had aroot diameter of 2 mm and a height of 4 mm, and were arranged atintervals (pitches) of 3 mm, the number of the columnar protrudingportions 110 b being 363 so that the columnar protruding portions 110 bhad a total surface area of 5405 mm² in Example 5, that the columnarprotruding portions 110 b had a tapered angle of 3° and a total surfacearea of 7447 mm² in Example 6, that the columnar protruding portions 110b had a root diameter of 2 mm, a height of 4 mm and a tapered angle of5°, and were arranged at intervals (pitches) of 3 mm, the number of thecolumnar protruding portions 110 b being 363 so that the columnarprotruding portions 110 b had a total surface area of 5065 mm² inExample 7, that the columnar protruding portions 110 b had a rootdiameter of 2 mm, a height of 4 mm and a tapered angle of 3°, and werearranged at intervals (pitches) of 3 mm, the number of the columnarprotruding portions 110 b being 363 so that the columnar protrudingportions 110 b had a total surface area of 5285 mm² in Example 8. Then,by the same method as that in Example 1, the releasability of the heatradiating plate was evaluated, and the surfaces of the heat radiatingplate and the mold were observed. As a result, it was possible torelease the heat radiating plate from the mold by no shock (Example 5),one shock (Example 6), one shock (Example 7) and no shock (Example 8),respectively. In Examples 5 through 8, there was no problem in theshapes of the flat plate portion and column protruding portions of theheat radiating plate, and the mold was not damaged.

Example 9

In order to produce a heat radiating plate having a similar shape tothat shown in FIGS. 5A and 5B, there was used a mold of carbon having asimilar shape to that of the mold 120 shown in FIGS. 4A through 4D,except that three ceramic substrate housing portions 122 c were arrangedat intervals of 1 mm and that the metal plate forming portion 122 d wasformed in each of the ceramic substrate housing portions 122 c. Therewere also prepared three ceramic substrates 214 of aluminum nitridehaving a size of 65 mm×60 mm×0.6 mm, and three reinforcing members 212of aluminum nitride having a size of 59 mm×110 mm×0.6 mm. Then, theceramic substrates 214 were arranged in the ceramic substrate housingportions 122 c of the lower mold member 122 of the mold 120, and bothend portions (having a length of 5 mm) of each of the reinforcingmembers 212 were arranged in the reinforcing member supporting portions122 b of the lower mold member 122, respectively, so that thereinforcing members 212 are spaced at intervals of 7 mm to substantiallyface the central portion of each of the ceramic substrates 214,respectively. Thereafter, the lower mold member 122 was covered with theupper mold member 124 of the mold 120 to be put in a furnace, and theinterior of the furnace was caused to be in an atmosphere of nitrogen todecrease the oxygen concentration therein to 4 ppm or less. In thisstate, the mold 120 was heated to 720° C. by the temperature control ofa heater, and then, a molten metal of aluminum having a purity of 99.9%,which was heated to 720° C. and previously measured, was poured into themold 120 from the injecting nozzle mounted on the inlet of the mold 120while being pressurized at 10 kPa by nitrogen gas to remove oxide filmson the surface of the molten metal. Thus, the molten metal was filled ina space having a size of 220 mm×100 mm×4 mm defined by the flat plateforming portion 122 a and the flat plate forming portion 124 a (having adepth of 0.7 mm) in the mold 120, and in the metal plate formingportions 122 d having a size of 62 mm×57 mm×0.4 mm via the molten metalpassage formed in the lower mold member 122. Thereafter, nitrogen gaswas blown into the inlet from the injecting nozzle to cool and solidifythe molten metal in the mold 120 while pressurizing the molten metal at10 kPa. Thus, by the so-called molten metal bonding method, there wasproduced a heat radiating plate wherein the reinforcing members 212passed through the flat plate portion 210 a in a region, in which onemajor surface of each of the reinforcing members 212 (the major surfaceon the side of the columnar protruding portions 210 b) was spaced fromone major surface of the flat plate portion 210 a (the major surface onthe side of the columnar protruding portions 210 b) by 0.7 mm, thereinforcing members 212 being bonded directly to the flat plate portion210 a, both end portions of each of the reinforcing members 212protruding from the side faces of the flat plate portion 210 a, wherein662 columnar protruding portions 210 b were arranged in each of regionsfacing the heating element mounting regions (the regions in which theceramic substrates 214 were bonded to the flat plate portion 210 a) onone major surface of the flat plate portion 210 a at intervals of 6 mm,each of the columnar protruding portions 210 b having a shape ofsubstantially circular truncated cone which had a root diameter (adiameter of a bottom face) of 2.5 mm, a height of 8 mm and a taperedangle of 2°, and wherein one major surface of each of the ceramicsubstrates 214 was bonded directly to the other major surface of theflat plate portion 210 a, and the metal plate 216 was bonded directly tothe other major surface of each of the ceramic substrates 214. After theheat radiating plate was ejected from the mold 120, the both endportions of the reinforcing members 212 in longitudinal directionsthereof, the end portions protruding from the flat plate portion 210 a,were removed (by dividing the both end portions by hand along breaklines previously formed by laser processing) to produce a heat radiatingplate 210 having a similar shape to that shown in FIGS. 5A and 5B.

Furthermore, when the heat radiating plate was ejected from the mold120, after the lower mold member 122 was detached, the upper mold member124 was fixed to a mold releasing apparatus, and a steel plate wasarranged on the upper mold member 124 so as to contact thereto. Then,the steel plate was knocked by a knocker (for quantitatively makingshocks on the mold to release the heat radiating plate from the mold) toevaluate the releasability of the heat radiating plate from the mold bythe number of shocks until release, and the surfaces of the heatradiating plate and the mold were observed. As a result, it was possibleto release the heat radiating plate from the mold by two shocks. Therewas no problem in the shapes of the flat plate portion and columnprotruding portions of the heat radiating plate, and the mold was notdamaged.

Examples 10-11

There was produced a heat radiating plate 210 by the same method as thatin Example 9, except that the columnar protruding portions 210 b had aroot diameter of 4 mm and a tapered angle of 5°, and were arranged atintervals of 12.5 mm, the number of the columnar protruding portions 210b being 252 in Example 10, that the columnar protruding portions 210 bhad a root diameter of 3 mm and a tapered angle of 3.5°, and werearranged at intervals (pitches) of 9 mm, the number of the columnarprotruding portions 210 b being 544 in Example 11. Then, by the samemethod as that in Example 9, the releasability of the heat radiatingplate was evaluated, and the surfaces of the heat radiating plate andthe mold were observed. As a result, it was possible to release the heatradiating plate from the mold by one shock in Examples 10 and 11. InExamples 10 and 11, there was no problem in the shapes of the flat plateportion and column protruding portions of the heat radiating plate, andthe mold was not damaged.

Comparative Examples 1-2

There was produced a heat radiating plate 110 by the same method as thatin Example 1, except that the distance between one major surface of thereinforcing member 112 (the major surface on the side of the columnarprotruding portions 110 b) and one major surface of the flat plateportion 110 a (the major surface on the side of the columnar protrudingportions 110 b) was 2.7 mm, the columnar protruding portions 110 bhaving a height of 5 mm, a tapered angle 5° and a total surface area of5018 mm² in Comparative Example 1 and that the distance between onemajor surface of the reinforcing member 112 (the major surface on theside of the columnar protruding portions 110 b) and one major surface ofthe flat plate portion 110 a (the major surface on the side of thecolumnar protruding portions 110 b) was 1.2 mm, the columnar protrudingportions 110 b having a height of 5 mm, a tapered angle 5° and a totalsurface area of 5018 mm² in Comparative Example 2. Then, by the samemethod as that in Example 1, the releasability of the heat radiatingplate was evaluated, and the surfaces of the heat radiating plate andthe mold were observed. As a result, it was not possible to release theheat radiating plate unless 15 shocks (Comparative Example 1) and 8shocks (Comparative Example 2) were made. In Comparative Examples 1 and2, flaws and deformations on the columnar protruding portions (radiatingfins) of the heat radiating plate were observed. Furthermore, althoughthe mold was not damaged, there is every possibility that the mold maybe damaged since the releasability was bad.

Comparative Example 3

There was produced a heat radiating plate 110 by the same method as thatin Example 1, except that the distance between one major surface of thereinforcing member 112 (the major surface on the side of the columnarprotruding portions 110 b) and one major surface of the flat plateportion 110 a (the major surface on the side of the columnar protrudingportions 110 b) was 1.3 mm. Then, by the same method as that in Example1, it was attempted to evaluate the releasability of the heat radiatingplate and to observe the surfaces of the heat radiating plate and themold. However, since it was not possible to release the heat radiatingplate from the mold after 30 shocks were made by the mold releasingapparatus, the heat radiating plate was released from the mold by hand.As a result, the upper mold member 124 was broken (it was not possibleto release the heat radiating plate from the mold unless the upper moldmember 124 was broken). In addition, flaws and deformations on thecolumnar protruding portions of the heat radiating plate were observed.

As described above, in Examples 1 through 11, the reinforcing member 112passing through the flat plate portion 110 a of the heat radiating plate110 from one end face of the flat plate portion 110 a in widthdirections (perpendicular to longitudinal directions) thereof to theother end face thereof to extend in the width directions was arranged ina region (a region close to a highest stress region between the heatradiating plate 110 and the mold 120) which was close to one majorsurface (a major surface on the side of columnar protruding portions 110b) of the flat plate portion 110 a of the heat radiating plate 110 sothat the thermal expansion coefficient of the one major surface (themajor surface on the side of the columnar protruding portions 110 b)approaches that of the mold 120. Therefore, even if the tapered angle ofthe columnar protruding portions (radiating fins) 110 b was small (notgreater than 5°), the releasability of the heat radiating plate 110 fromthe mold 120 was good, and it was possible to form good heat radiatingfins having excellent dimensional accuracy while it was possible toprevent the mold 120 of carbon from being damaged.

While the present invention has been disclosed in terms of the preferredembodiment in order to facilitate better understanding thereof, itshould be appreciated that the invention can be embodied in various wayswithout departing from the principle of the invention. Therefore, theinvention should be understood to include all possible embodiments andmodification to the shown embodiments which can be embodied withoutdeparting from the principle of the invention as set forth in theappended claims.

1-19. (canceled)
 20. A heat radiating plate which is made of a metalmaterial and which comprises: a flat plate portion; a plurality ofcolumnar protruding portions which protrude from one surface of the flatplate portion and which are integrated with the flat plate portion; anda reinforcing plate member which extends in directions parallel to onesurface of the flat plate portion, the reinforcing plate member beingarranged inside the flat plate portion between the one surface and anopposite surface of the flat portion, the reinforcing plate member beingcloser to the one surface than the opposite surface of the flat portionso as to be closer to the plurality of columnar protruding portions thanthe opposite surface of the flat plate portion, and the reinforcingplate member being apart from the one surface of the flat plate portionby 20% or less of a thickness of the flat plate portion.
 21. The heatradiating plate as set forth in claim 1, wherein said reinforcing platemember passes through said flat plate portion to extend therein.
 22. Theheat radiating plate as set forth in claim 1, wherein said reinforcingplate member has end faces which are exposed to the outside, and thewhole surface of said reinforcing plate member except for the end facesis bonded directly to said flat plate portion.
 23. The heat radiatingplate as set forth in claim 1, wherein said reinforcing plate member ismade of a material which has a higher melting point than that of saidmetal material.
 24. The heat radiating plate as set forth in claim 1,wherein said metal material is aluminum or an aluminum alloy.
 25. Theheat radiating plate as set forth in claim 5, wherein said reinforcingplate member is made of a metal which contains iron and at least oneselected from a group consisting of nickel, cobalt, copper andmanganese.
 26. The heat radiating plate as set forth in claim 5, whereinsaid reinforcing plate member is made of at least one ceramic selectedfrom a group consisting of alumina, aluminum nitride, silicon nitrideand silicon carbide.
 27. The heat radiating plate as set forth in claim1, wherein said reinforcing plate member is apart from said one surfaceof said flat plate portion by 0.1 to 1.0 mm.
 28. The heat radiatingplate as set forth in claim 1, wherein one surface of a ceramicsubstrate is bonded directly to said opposite surface of said flat plateportion, and a metal plate is bonded directly to an opposite surface ofsaid ceramic substrate.
 29. The heat radiating plate as set forth inclaim 1, wherein each of said columnar protruding portions has a shapeof cylindrical or circular truncated cone.
 30. The heat radiating plateas set forth in claim 1, wherein each of said columnar protrudingportions extends in directions perpendicular to the one surface of saidflat plate portion.
 31. The heat radiating plate as set forth in claim1, wherein each of said columnar protruding portions has a bottom facehaving a diameter of 1 to 10 mm and a height of about 2 to 50 mm andwherein a distance between the central lines of adjacent two of saidcolumnar protruding portions is 2 to 10 mm, and an angle between thecentral line of each of said columnar protruding portions and the sideface thereof is 0.5 to 5°, the number of said columnar protrudingportions being 20 to
 1000. 32. A method for producing a heat radiatingplate which is made of a metal material and which has a flat plateportion and a plurality of columnar protruding portions protruding fromone surface of the flat plate portion and being integrated with the flatplate portion, said method comprising the steps of: allowing endportions of a reinforcing plate member of a material, which has a highermelting point than that of said flat plate portion and said columnarprotruding portions, to be supported on a mold; injecting a molten metalof a metal material into the mold so that the molten metal contacts thewhole surface of the reinforcing plate member except for end portionsthereof in the mold; and then, cooling and solidifying the molten metalfor forming the flat plate portion and the plurality of columnarprotruding portions, which protrude from the one surface of the flatplate portion and which are integrated with the flat plate portion, andfor allowing the reinforcing plate member, which extends parallel to theone surface of the flat plate portion, to be arranged inside the flatplate portion between the one surface and an opposite surface of theflat portion and to be closer to the one surface of the flat plateportion than the opposite surface of the flat portion so as to be apartfrom the one surface of the flat plate portion by 20% or less of athickness of the flat plate portion, while allowing the reinforcingplate member to be bonded directly to the flat plate portion.
 33. Amethod for producing a heat radiating plate which is made of a metalmaterial and which has a flat plate portion and a plurality of columnarprotruding portions protruding from one surface of the flat plateportion and being integrated with the flat plate portion, the othersurface of the flat plate portion being bonded directly to one surfaceof a ceramic substrate, said method comprising the steps of: allowingend portions of the ceramic substrate and end portions of a reinforcingplate member of a material, which has a higher melting point than thatof said flat plate portion and said columnar protruding portions, to besupported on a mold so that the ceramic substrate is apart from thereinforcing plate member in the mold; injecting a molten metal of ametal material into the mold so that the molten metal contacts bothsurface of the substrate and the whole surface of the reinforcing platemember except for end portions thereof in the mold; and then, coolingand solidifying the molten metal for forming a metal plate to allow themetal plate to be bonded directly to the other surface of the ceramicsubstrate, and for forming the flat plate portion and the plurality ofcolumnar protruding portions, which protrude from the one surface of theflat plate portion and which are integrated with the flat plate portion,and for allowing the reinforcing plate member, which extends parallel tothe one surface of the flat plate portion, to be arranged inside theflat plate portion between the one surface and an opposite surface ofthe flat portion and to be closer to the one surface of the flat plateportion than the opposite surface of the flat portion so as to be apartfrom the one surface of the flat plate portion by 20% or less of athickness of the flat plate portion, while allowing the reinforcingplate member to be bonded directly to the flat plate portion.
 34. Themethod for producing a heat radiating plate as set forth in claim 13 or14, wherein said end portions of said reinforcing plate memberprotruding from said flat plate portion are removed.
 35. The method forproducing a heat radiating plate as set forth in claim 13, wherein saidmold comprises an upper mold member and a lower mold member, and saidend portions of said reinforcing plate member are clamped between theupper mold member and the lower mold member to be supported on saidmold.
 36. The method for producing a heat radiating plate as set forthin claim 13, wherein said molten metal is a molten metal of aluminum oran aluminum alloy.
 37. The method for producing a heat radiating plateas set forth in claim 17, wherein said reinforcing plate member is madeof a metal which contains iron and at least one selected from a groupconsisting of nickel, cobalt, copper and manganese.
 38. The method forproducing a heat radiating plate as set forth in claim 17, wherein saidreinforcing plate member is made of at least one ceramic selected from agroup consisting of alumina, aluminum nitride, silicon nitride andsilicon carbide.
 39. The method for producing a heat radiating plate asset forth in claim 13, wherein said reinforcing plate member is apartfrom said one surface of said flat plate portion by 0.1 to 1.0 mm. 40.The method for producing a heat radiating plate as set forth in claim13, wherein each of said columnar protruding portions has a shape ofcylindrical or circular truncated cone.
 41. The method for producing aheat radiating plate as set forth in claim 13, wherein each of saidcolumnar protruding portions extends in directions perpendicular to theone surface of said flat plate portion.
 42. The method for producing aheat radiating plate as set forth in claim 13, wherein each of saidcolumnar protruding portions has a bottom face having a diameter of 1 to10 mm and a height of about 2 to 50 mm and wherein a distance betweenthe central lines of adjacent two of said columnar protruding portionsis 2 to 10 mm, and an angle between the central line of each of saidcolumnar protruding portions and the side face thereof is 0.5 to 5°, thenumber of said columnar protruding portions being 20 to 1000.